Portuguese explorer, discoverer of the Cape of Good Hope, was probably a kinsman of Joćo Diaz, one of the first Portuguese to round Cape Bojador (1434), and of Diniz Diaz, the discoverer of Cape Verde (1445). In 1478 a Bartholomeu Diaz, probably identical with the discoverer, was exempted from certain customary payments on ivory brought from the Guinea coast. In 1481 he commanded one of the vessels sent by King Joćo II. under Diogo d'Azambuja to the Gold Coast. In 1486 he seems to have been a cavalier of the king's household, and superintendent of the royal warehouses; on the 10th of October in this year he received an annuity of 6000 reis from Joćo for "services to come"; and some time after this (probably about July or August 1487, rather than July 1486, the traditional date) he left Lisbon with three ships to carry on the work of African exploration so greatly advanced by Diogo Cćo (1482-86). Passing Cćo's farthest point near Cape Cross, he erected a pillar on what is now known as Diaz Point, south of Angra Pequena or Lüderitz Bay; of this fragments still exist. From this point (according to De Barros) Diaz ran thirteen days southwards before strong winds, which freshened to dangerous stormy weather, in a comparatively high southern latitude, considerably south of the Cape. When the storm subsided the Portuguese stood east; and failing, after several days search, to find land, turned north, and so struck the south coast of Cape Colony at Mossel Bay (Diaz' Bahia dos Vaqueiros), halfway between the Cape of Good Hope and Port Elizabeth (February 3, 1488). From there they coasted eastward, passing Algoa Bay (Diaz' Bahia da Roca), erecting pillars or perhaps wooden crosses, it is said, on one of the islands in this bay and at or near Cape Padrone farther east; of these no traces remain. The officers and men now began to insist on return, and Diaz could only persuade them to go as far as the estuary of the Great Fish River (Diaz' Rio do Iffante, so named from his colleague, Captain Joćo Iffante). Here, however, halfway between Port Elizabeth and East London (and indeed from Cape Padrone), the north-easterly trend of the coast became unmistakable; the way around Africa had been laid open. On his return Diaz perhaps named Cape Agulhas after St Brandan; while on the southernmost projection of the modern Cape peninsula, whole remarkable highlands (Table Mountain, etc.) doubtless impressed him as the practical termination of the continent, he bestowed, says De Barros, the name of Cape of Storms (Cabo Tormentoso) in memory of the storms he had experienced in these far southern waters; this name was changed by King Joćo to that of Good Hope (Cabo da Boa Esperanēa). Some excellent authorities, however, make Diaz himself give the Cape its present name. Hard by this "so many ages unknown promontory" the explorer probably erected his last pillar. After touching at the Ilha do Principe (Prince's Island, southwest of the Cameroons) as well as at the Gold Coast, he appeared at Lisbon in December 1488. He had discovered 1260 miles of hitherto unknown coast; and his voyage, taken with the letters soon afterwards received from Pero de Covilhćo (who by way of Cairo and Aden had reached Malabar on one side and the "Zanzibar coast" on the other as far south as Sofala, in 1487-88) was rightly considered to have solved the question of an ocean route around Africa to the Indies and other lands of South and East Asia.

No record has yet been found of any adequate reward for Diaz; on the contrary, when the great Indian expedition was being prepared (for Vasco da Gama's future leadership) Bartolomeu only superintended the building and outfit of the ships; when the fleet sailed in 1497, he only accompanied da Gama to the Cape Verde Islands, and after this was ordered to El Mina on the Gold Coast. On Cabral's voyage of 1500 he was indeed permitted to take part in the discovery of Brazil (April 22), and thence should have helped to guide the fleet to India; but he perished in a great storm off his own Cabo Tormentoso. Like Moses, as Galvano says, he was allowed to see the Promised Land, but not to enter in.